The present invention relates to a magnetic head for writing/reading to/from a magnetic recording medium, and a manufacturing method therefor.
A magnetic disk drive uses a magnetic head to write/read data to/from a recording medium. Increasing the recording capacity per unit area of the magnetic disk requires increasing the areal density. However, the conventional longitudinal recording system has a problem in that the areal density cannot be increased due to thermal fluctuations attributed to magnetization of the medium when the bit length of written data is small.
There is a recording technique called “perpendicular recording” which does not cause the above problem. The perpendicular recording system writes a magnetization signal to the disk medium in a direction perpendicular to the surface of the disk. To read data from the medium, the perpendicular recording system, like the longitudinal recording system, can use a head such as: a giant magneto-resistive (GMR) head; a tunneling magneto-resistive (TMR) head, which produces higher read output power; or a CPP (current perpendicular to the plane) type GMR head, which produces a current flowing perpendicular to the film surface. To write data to the medium, on the other hand, the perpendicular recording system must use a single-pole magnetic head. Also in perpendicular recording, increasing the areal density requires increasing the track density and linear recording density. To increase the linear recording density, it is necessary to improve the recording magnetic field gradient of the write head. To accomplish this, the recording medium may have a two-layer structure in which the under layer is a soft under layer (SUL). To enhance the track density, on the other hand, the magnetic head must be formed to have a very small and precise track width.
It should be noted that in the case of perpendicular magnetic recording, the main magnetic pole piece portion of the write head must be protected by an insulating layer to maintain sufficient write performance. For example, patent document 1 (Japanese Patent Laid-Open No. Hei 8-87715) discloses a magnetic head for perpendicular magnetic recording in which a magnetic film having high specific resistance is formed around the main magnetic pole piece for insulation.